A standard ball-bolt chuck has a chuck body rotatable about a main axis and a plurality of jaw holders angularly spaced about the axis, fixed axially on the chuck body, and each having radially displaceable outer and inner ends. Jaws are bolted to the outer ends. A piston axially displaceable in the body is coupled via cam formations with the jaw-holder inner ends for radially displacing the jaw-holder outer ends on axial displacement of the piston. Thus the piston can shift to move the jaws carried on the holders radially inward or outward, depending on whether the chuck is used for outside or inside holding, to radially grip and hold a workpiece.
Such a chuck can adapt limitedly to an irregularly shaped workpiece and can grip with great radial force. Nonetheless it is still possible for the workpiece to shift on the chuck, in particular axially.